Saving the data to backend by self id

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error:Specified cast is not valid

this is my code.........

C#

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace saving_data_backend
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            SqlConnection con = new SqlConnection();
            con.ConnectionString = "Data Source=CIODEV03\\SQLEXPRESS;
            Initial Catalog=EmployeeDB;
            Integrated Security=True";
            try
            {
                //create  a sql command to get a unique contactID.

                SqlCommand cmd = new SqlCommand("Select MAX(cemployeeCode) from 
                                                               employee2", con);
                // Open the database connection
                con.Open();

                //Execuete the sql command 
                int intNextID = (int)cmd.ExecuteScalar() + 1;

                //Create a command to add a new row...

                SqlCommand cmd1 = new SqlCommand(String.Format("Insert into 
                        employee2 (cemployeeCode,Name,Age) values
                      ({0},'{1}','{2}')", intNextID, textBox1.Text,
                       textBox2.Text), con);

                //Execute the command 
                if (cmd1.ExecuteNonQuery() > 0)
                {
                    label1.Text = "Record Added";
                    textBox1.Text = "";
                    textBox2.Text = "";
                }
                else
                {
                    label1.Text = "Couldn't add record";
                }
            }
            catch (Exception ex)
            {
                label1.Text = "Error:" + ex.Message;
            }
            finally
            {
                //close the con.
                con.Close();
            }
        }
    }
}

and my database is.......

SQL

cempcode(PK,int NOT NULL)
Name (nvarchar(50) NULL)
Age (nvarchar(50) NULL)

Posted 9-Feb-12 21:05pm

rockpune

Updated 9-Feb-12 21:14pm

Lakamraju Raghuram

v2

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Comments

walterhevedeich 10-Feb-12 3:31am

Have you just mistyped cempcode instead of cemployeeCode?

manognya kota 10-Feb-12 3:33am

Did u put a breakpoint and check where exactly is the error occuring?

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OriginalGriff · Answer 1 · 2012-02-09T21:34:00

Don't do it like that!
Do not concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Use Parametrized queries instead.

SQL

SqlCommand cmd1 = new SqlCommand(String.Format("Insert into employee2 (cemployeeCode,Name,Age) values
                      (@ID, @NAME, @AGE"), con);
cmd1.Parameters.AddWithValue("@ID", intNextID);
cmd1.Parameters.AddWithValue("@NAME", textBox1.Text);
cmd1.Parameters.AddWithValue("@AGE", textBox2.Text);

That may fix your problem.

But what you are doing there is very, very dangerous.
The only reason for using SQL is to work in a multiuser environment.
What happens if two users try to add a record at the same time? They will both try to insert the same ID!

Either use an Identity spec in your ID column (and let the DB handle assigning a value), or use a Guid instead - there are other ways but those are the easiest.